Summary of Lecture 1

Summary of Lecture 1

• Introduction to Earth’s atmosphere– origin– composition– structure– comparison with other planets

• Stefan’s law

44 1sT S

Solar and Terrestrial Radiation

Sun ~ 6000 K

UV/vis max~0.6m

Solar flux =1370 Wm-2

S (1-)/4=TE4

Earth ~ 255 K

IR max~ 12m

UV absorptionInfraRed

UVa /Visible

UVb

UVc

DUV

Absorption by atmospheric gases

Solar energy received

Radiation Balance

Notes:• Surface has Ts=288 K and radiates Ts

4 = 400 Wm-2 (117 units).

• Atmosphere at 250 K radiates 220 Wm-2 (64 units), both up and down.

• 30% of surface radiation is reflected by the atmosphere (32 units), giving a total downward flux of 96 units.

• Non-radiative flux of 100 Wm-2 (30 units) drives the atmospheric circulation and weather

Seasonal net IR radiation

Global Climate

Net short, long and global radiation entering and leaving the top of our atmosphere measured by satellite.

Data are from the Earth Radiation Budget Experiment (ERBE)

Global Warming

Global temperatures 1880-2015

Change in extent of Arctic sea ice

Rising CO2 levels

0

50

100

150

200

250

300

350

1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

700

600

500

400

350

CO

2 c

on

cen

trati

on

p

pm

Carbon dioxide concentrationin the atmosphere, due to three emissions scenarios

Business as usual emissionsConstant 1990 emissions50% reduction in emissions

Global temperature riseG

lob

al t

em

pe

ratu

re r

ise,

deg

ree

s C IPCC A1FI emissions

A2 emissionsB2 emissionsB1 emissions

Components of sea-level rise

Hadley Centre

Pattern of annual temperature changes

2080s relative to present dayA1FI emissions scenario

0 1 2 3 4 5 6

Met Office / Hadley Centre

Temperature riseMedium-high emissions scenario, 2080s

winter summer

°C

Hadley Centre Hadley Centre

Pattern of annual precipitation changes

2080s relative to present day

–3 –2 –1 1 2 3–0.5 0.5–0.25 0.250

A1FI emissions scenarioMet Office / Hadley Centre

Change in precipitation

%

winter summer

Medium-high emissions scenario, 2080s

Hadley Centre Hadley Centre

Change in surface temperature with forced THC collapse, but without change in greenhouse

gases

Deg C

Hadley Centre